Fluidized bed granulation

ABSTRACT

Method and fluidized bed reactor for the production of granules, such as granules of urea or ammonium nitrate. The fluidized bed reactor comprises at least one granulation compartment with air inlets, and an air moving device downstream of the granulation compartment, e.g., downstream of at least one scrubbers. The air moving device is configured to draw air through said at least one air inlet into at least one granulation compartment.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to European PatentApplication No. EP16196033.1, filed Oct. 27, 2016. The disclosure of theprior application is hereby incorporated in its entirety by reference.

FIELD OF THE INVENTION

This invention relates to a fluidized bed reactor, as well as to amethod for the production of granules, such as urea or ammoniumnitrate-based granules, typically used as a fertilizer material, usingsuch a fluidized bed reactor.

BACKGROUND

The discussion below is merely provided for general technologicalbackground information and is not intended to be used as an aid indetermining the scope of the claimed subject matter.

To produce granules of a liquid solution or melt, such as an aqueous ornon-aqueous ammonium nitrate or urea solution, said solution or melt issprayed into a granulation compartment containing a fluidized bed ofsolid nuclei. The fluidized bed is fluidized by introducing afluidization gas, usually air, through the bed of nuclei. The nucleigrow by accretion, i.e. solidification and crystallization of thesprayed urea liquid on them, to form granules of a desired average size,which are subsequently withdrawn from the fluidized bed reactor, alsocalled a granulation reactor or granulator, wordings which are usedinterchangeably in this patent document.

The fluidization air is generally blown into the granulationcompartments by means of blowers. In a subsequent compartment, the airis stripped from fine solid material, e.g., in a scrubber, a cyclone ora similar separator. The air is usually removed from the granulationreactor by means of an exhaust fan.

An example of such reactor for the production of urea granules isdisclosed in U.S. Pat. No. 3,533,829 (Azote et Produits Chimiques S.A.,1970), which discloses a fluidized bed reactor comprising at least onegranulation compartment with at least one air inlet and which comprisestwo air moving devices: (i) a blower upstream of the fluidized bedconfigured to push fluidizing air through said at least one air inletinto the granulation compartment, and (ii) an exhaust fan, downstream ofthe granulation compartment, but not configured to draw air through theat least one air inlet into the granulation compartment; the exhaust fanmerely serves the exhaustion of air leaving the system.

Also GB2046121 (MTA Müszaki Kémiai, 1980) discloses a fluidized bedreactor comprising at least one granulation compartment with at leastone air inlet and which comprises two air moving devices: (i) a blowerupstream of the fluidized bed configured to push fluidizing air throughsaid at least one air inlet into the granulation compartment, and (ii)an exhaust fan, downstream of the granulation compartment, configured toremove air leaving the system, but not configured to draw air throughthe at least one air inlet into the granulation compartment; the exhaustfan merely serves the exhaustion of air leaving the wet scrubber, whichis positioned after the fluidized bed reactor.

The produced granules are generally moved from the granulationcompartment to an after-cooler, which can be integrated with thefluidized bed reactor. In the after-cooler, further dust is produced.Therefore, also air from the after-cooler is usually first treated in ascrubber before it can be vented.

To avoid leakage of air from the reactor, a slight underpressure,typically of about 0.1 to 10 mbar, preferably about 0.1 to 7 mbar, iscreated in the fluidized bed reactor compartment and/or after-cooler, asfor example is disclosed in U.S. Pat. No. 5,779,945 (DSM N.V., 1998) andEP 2253374 A1 (Stamicarbon, 2010).

SUMMARY OF THE INVENTION

It is an object of the invention to improve process efficiency whilereducing energy consumption.

The object of the invention is achieved with a fluidized bed reactorcomprising at least one granulation compartment with at least one airinlet and at least one air moving device, configured to move air throughsaid at least one air inlet into said at least one granulationcompartment, wherein said air is moved essentially by the action of saidat least one air moving device downstream of said granulationcompartment. To this end, the at least one air moving devices downstreamof said at least one granulation compartment has a total capacity togenerate a vacuum in the at least one granulation compartment, exceedingthe total pressure drop between the air inlets and the downstream airmoving devices. For example, the at least one air moving devices may beconfigured to create a vacuum of at least about 50 mbar, e.g., withinthe range of about 50 to about 70 mbar.

Where known systems use blowers to blow air into the granulationcompartment, it was surprisingly found that a fluidized bed reactorwhich draws air by a downstream air moving device (e.g. an air pump,ventilator, or fan) consumes substantially less energy, since thefluidized bed reactor can now be designed for lower inlet temperaturesof the fluidization air.

This is especially useful for the production of urea-based products asthe process of making urea is an exothermal process, but the features ofthe fluidized bed reactor according to the invention and the methodaccording to the invention are equally beneficial for the production ofammonium nitrate. During crystallization of the urea liquid, collectedon the solid nuclei, heat is generated. Air, used for fluidization,removes excess heat from the fluidized bed. The required amount offluidization air depends on the temperature of the air, entering thegranulator compartment. The warmer the fluidization air is when enteringthe granulation compartment, the more fluidization air is required toremove excess heat from the granulation compartment. As a result, moreair has to be cleaned in the scrubbers and more energy is consumed bythe exhaust fans. Therefore, the temperature of the fluidization airshould not be too high. If the temperature of the fluidization air islow, less air is required for cooling the fluidized bed. However, theinflow of fluidization air must not be too low, otherwise the bed ofnuclei will not be sufficiently fluidized. Hence, the fluidized bedreactor should be designed in such a way that, on the one hand, theamount of fluidization air must be sufficient to achieve goodfluidization and to cool the fluidized bed effectively, while, on theother hand, energy consumption for cleaning and discharging exhaust airshould be minimized. Alternatively, the fluidization air may be cooledby air cooling equipment, but this setup requires extra energy to drivethe air cooling equipment.

Air used for fluidization may, for example, be ambient air. Thetemperature of the ambient air may differ considerably. The fluidizedbed reactor is therefore usually designed for use with air of summertimetemperatures. With known fluidized bed reactors, these temperatures areincreased with about 5 to 9° C., or even more, because of the heat,generated by the blowers, as these blowers, blowing the fluidization airinto the granulation compartments, also generate heat. The generatedheat is typically dependent on the efficiency of the used blower and onthe pressure at the outlet of the blower. In practice, the generatedheat is such that the passing air is heated by at least 5° C., normallyat least 9° C., and sometimes 11° C. or more above ambient temperature.

As a result, known fluidized bed reactors are designed for use withrelatively high temperatures of the fluidization air. This results inhigher energy consumption by the blower, the scrubbers and the exhaustfans. Moreover, in winter, the ambient air should be pre-heated to bringit closer to the relatively high air temperature for which the reactorwas designed.

With the fluidized bed reactor of the present invention, no upstream airmoving devices need to be used at the fluidization air inlet, but theair is drawn into the granulation compartment by means of at least onedownstream air moving device. This means that the fluidization air isnot heated by any upstream blower and the reactor can be designed forlower inlet temperatures of the fluidization air. Less air needs to beconsumed for cooling the fluidized bed and less air needs to be scrubbedand discharged. Moreover, lower pre-heating temperatures can be used inwinter.

With the fluidized bed reactor of the present invention, using one ormore downstream air moving devices to draw air into the reactor,automatically, an underpressure in the granulation compartments isachieved, while with the known fluidized bed reactors, an overpressureis automatically realized and extra measures need to be taken to realizea slight underpressure at the granulation compartment. An underpressureresults in an improved evaporation in the granulation compartment.

According to one embodiment, a fluidized bed reactor according to theinvention is provided, devoid of any air moving device which isconfigured to move air through said at least one air inlet into saidgranulation compartment and which is positioned upstream of thegranulation compartment.

According to one embodiment, a fluidized bed reactor according to theinvention is provided comprising at least one after-cooler, wherein theat least one air moving device is positioned downstream of the at leastone after-cooler. As a result, the air entering the after-cooler is notheated by the air moving device motor, such that the air is alreadyabout 9 toll ° C. cooler when it enters the after-cooler. By eliminatingthe 9 to 11° C. extra heating of the fluidization air by the air movingdevice motor, the cooler can operate, e.g., with an ambient airtemperature. This means a substantial improvement of the coolingcapacity.

According to one embodiment, the fluidized bed reactor comprises atleast one after-cooler positioned downstream from the at least onegranulation compartment. The after-cooler(s) is generally part of thefluidized bed reactor and is also provided with a supply of fluidizationair. In some embodiments, the fluidized bed reactor comprises at leasttwo after-coolers. In some embodiments, the fluidized bed reactorcomprises two or three after-coolers. The at least one air movingdevices downstream of the after-cooler(s) may be configured to drawfluidization air also into the after-cooler, optionally into both theafter-cooler and the granulation compartment.

According to one embodiment, the at least one after-cooler is integratedin the fluidized bed reactor as a set of at least two chamberssubsequent to the granulation compartments.

According to one embodiment, the at least one granulation compartmentand the at least one after-cooler are separated by one or more ducts orchannels and are not present in a single unit.

According to another embodiment, at least one granulation compartmentand at least one after-cooler compartment are integrated together in thesame unit and are not separated by a duct or channel. In one embodiment,all of the granulation compartment(s) and after-cooler(s) are integratedtogether in a single unit, wherein the after-cooler(s) are positioneddownstream from the granulation compartment(s). These embodimentsprovide for a more compact design. It is surprising and unexpected thatsufficient and acceptable cooling may be accomplished when thegranulation compartment(s) and after-cooler(s) are combined together.

According to one embodiment, the granulation compartment can be, forexample, a spouted bed or any other suitable type of fluidized bed.Combinations of different types can also be used. In some embodiments,the fluidized bed reactor comprises at least two granulationcompartments. In some embodiments, the fluidized bed reactor comprisesthree or four granulation compartments.

According to one embodiment, the fluidized bed reactor may comprise atleast one scrubber downstream of the at least one granulationcompartment. In such a case, the at least one air moving device fordrawing fluidization air into the granulation compartment may, forexample, be positioned downstream of the at least one scrubber. The airmoving device may, for example, comprise at least one exhaust fan, inparticular an exhaust of the scrubber.

According to another embodiment, the fluidized bed reactor may compriseat least one scrubber downstream of the at least one after-cooler. Insuch a case, the at least one air moving device for drawing fluidizationair into the granulation compartment may, for example, be positioneddownstream of the at least one scrubber. The air moving device may, forexample, comprise at least one exhaust fan, in particular an exhaust ofthe scrubber, in particular for discharging air.

A single scrubber can be used for scrubbing air from the at least oneafter-cooler and air from the at least one granulation compartment.

Alternatively, a first scrubber with at least one downstream air movingdevices can be used for the granulation compartments, while a secondscrubber or set of scrubbers, with at least one downstream air movingdevices can be used for the after-cooler.

The pressure drop over the scrubbers is preferably low. To this end,scrubbers may be used comprising vertical demisters.

Particularly low pressure drop can be obtained by using a serialarrangement of a first demister for coarse particles (typically having apressure drop of less than about 2 mbar) and a second demister for finerparticles, e.g., submicron particles. If the air between the demistersis cooled, condensation of moisture will enlarge the particles such thatthe second demister can also be of a low pressure drop type. A suitableconfiguration of scrubbers is, for example, disclosed in US patentapplication US 2015/0217221 (Green Granulation Technology, 2015),incorporated herein by reference in its entirety. Other configurationswith or without scrubbers can also be used.

The invention also relates to a method for the production of granules,such as granules of urea or ammonium nitrate, using the fluidized bedreactor according to the invention, as disclosed above.

According to one embodiment, a method is provided for the production ofgranules using a fluidized bed reactor comprising at least onegranulation compartment with at least one air inlets and at least oneair moving device, configured to move air through said at least one airinlet into said at least one granulation compartment, wherein said airis moved essentially by the action of said at least one air movingdevice downstream of said granulation compartment, the methodcomprising: drawing air in the at least one granulation compartmentthrough the at least one air inlet using the at least one air movingdevice; and fluidizing the bed of granules with said drawn in air.

According to one embodiment, the method is devoid of any air moving stepby an air moving device which is configured to move air through said atleast one air inlet into said granulation compartment and which ispositioned upstream of the granulation compartment.

Fluidization air is sucked into the granulation compartment by thedownstream air moving device, e.g., by creating a vacuum, exceeding thepressure drop between the at least one air inlet and the at least oneair moving device. The underpressure may, for example, be at least about50 mbar, e.g., in the range of about 50 to about 70 mbar.

The fluidized bed reactor can, for example, be configured such that thepressure drop between at least one air inlet and an air exhaust ofbetween 10 and 100 mbar, preferably less than about 80 mbar. Thepressure drop over the granulation compartment may, for example, bebetween 10 and 60 mbar, preferably less than about 50 mbar.

The temperature of the fluidization air entering the granulationcompartment may, for example, be below 114° C., e.g., below 100° C.,e.g., below 90° C. A spouted bed can for example be operated at or below120° C.

According to one embodiment, the air drawn into the at least onegranulation compartment is not preheated, either deliberately usingpre-heating equipment, or as a side effect of the action of upstreamequipment, such as a fan.

The granulation compartments may further comprise a plurality ofsprayers, connected to a supply of a granulating liquid, such as anaqueous urea solution. The sprayers may, for example, be configured tospray the liquid in at least one spraying zones in the compartment nextto at least one unsprayed zone. The sprayers can, for example, beatomizers or hydraulic sprayers, such as air-assisted hydraulicsprayers.

When the solution is sprayed into the granulator compartment, thesolution may, for example, have a temperature substantially above thecrystallization point. If the solution is a urea-based solution, thesolution can, for example, be sprayed at a temperature of at least about120° C., or at least about 130° C. or at least about 135° C. If thesolution is an ammonium nitrate solution, the solution can, for example,be sprayed at a temperature of at least about 160° C., or at least about170° C. or at least about 180° C. The solution can, for example, besprayed under a hydrostatic pressure of 1.5 to 6 bar, e.g., 2 to 4 baror other suitable pressures. The sprayed droplets can, for example, havean average droplet size of about 20 to 120 micrometer, e.g., about 30 to60 micrometer.

For granulation of urea, highly concentrated solutions can be used, forexample, with a urea content of at least 90 weight % by total weight ofthe urea solution, e.g., at least 95 weight %.

The water content of the urea solution is generally low, e.g., less than5 weight %, by total weight of the urea solution, e.g., less than 3weight %. If the water content is less than 2.5 weight %, the solutionis often referred to as a urea melt.

The urea solution may further contain additives such as, for example,formaldehyde and/or a urea-formaldehyde condensation products as agranulating aid for slowing down crystallization of the urea and as ananti-caking agent, preventing agglomeration of the resultant granules.If for example 0.1 to 3 weight %, based on total the weight of the ureasolution, of formaldehyde is added to the urea aqueous solution,atomized liquid droplets adhere better to the urea nuclei. Othersuitable additives can also be used.

For the granulation of ammonium nitrate, Mg(NO3)₂ and aluminiumsulphate, e.g., with NaOH, may be used as suitable additives.

The nuclei can be supplied to the fluidized bed reactor via at least oneinlet at an inlet side of the fluidized bed reactor. The nuclei caneither be supplied continuously or be supplied and processed per batch.

Before being submitted to the granulation process, the nuclei may haveany suitable average particle size, generally about at least 0.2, or atleast 0.5 mm, generally at most 6 mm.

The nuclei may have any suitable composition. In general, they willmainly comprise the same material as the crystallized granulatingliquid, in particular crystallized urea, but is also possible to usenuclei of a different composition than the crystallized granulatingliquid.

For granulating urea, the flow velocity of the fluidization air in thefluidized bed can, for example, be about 1 to 8 m/sec, e.g., at leastabout 2 and/or at most about 3 or 4 m/sec. For granulating ammoniumnitrate, the flow velocity of the fluidization air in the fluidized bedcan, for example, be about 1 to 8 m/sec, e.g., at least about 2 and/orat most about 3.5 or 4.5 m/sec.

For granulating urea, the temperature in the granulation compartments ofthe fluidized bed reactor can, for example, be between 90 and 120° C.,e.g., between 100 and 106° C. For granulating ammonium nitrate, thetemperature in the granulation compartments of the fluidized bed reactorcan, for example, be between 110 and 140° C., e.g., between 125 and 130°C. Typically, the temperature in the first compartment will be lower dueto the return flow of recycled material. This can be compensated byusing a higher density of sprayers in the first compartment.

To reduce the pressure drop over the granulation bed, the granulationbed may, for example, have a bed level of 1.5 m or less, e.g., about 1 mor less. Lower bed levels may reduce circulation of the granules in thefluidized bed. A suitable manner to reduce the bed level whilemaintaining the required circulation of granules is to use a fluidizedbed reactor comprising at least one compartment with a floor with airinlet openings and a plurality of sprayers for spraying a granulatingliquid, the sprayers being configured to spray the liquid in sprayingzones next to unsprayed zones of the fluidized bed. The alternatingarrangement of sprayed zones and unsprayed zones intensifies therequired circulation of the granules and increases the residence time.Examples of such fluidized bed reactors are disclosed in US 2015/0217248(Green Granulation Technology, 2015), incorporated herein by referencein its entirety.

The processed granules are typically discharged via at least one outletof the fluidized bed reactor, either continuously or per batch. Theprocessed granules typically have an average particle size of about 2 to4 mm, but can be made smaller or larger if so desired.

The water content of the granules can be kept well below 0.3 weight % bytotal weight of the granules, e.g., below 0.25 weight %.

Granules with a particle size below and/or above a given size limit, oragglomerates, can be separated from the outflow, e.g. by sieving.Optionally, the coarse particles and/or agglomerates can be crushed andrecycled to the fluidized bed reactor, e.g., together with granules witha particle size considered to be too small and/or with materialseparated from air discharged from the fluidized bed reactor.

The fluidized bed reactor can have at least one granulator compartmentsin a serial and/or parallel arrangement. In a specific embodiment, thefluidized bed reactor has at least two, e.g., three or more seriallyarranged compartments.

The inlets for fluidization air may, for example, comprise inlets infloors of the granulator compartments. To this end, the floor can forexample be a grid above an air supply.

Optionally, the fluidized bed reactor may comprise an after-cooler, suchas a fluidized bed cooler receiving discharged granules from thefluidized bed reactor compartments. The after-cooler can for example beused to cool the granules to a temperature of about 40° C.

The method according to the invention is suitable for the production ofgranules for agricultural and non-agricultural application, inparticular for the production of fertilizers, such as NP, NPK, calciumnitrate and ammonium nitrate-based fertilizers, as well as for theproduction of technical nitrates (explosives, etc.).

The method according to the invention is suitable for the production ofammonium nitrate-based granules, such as granules of ammonium nitrateand calcium nitrate.

The method according to the invention is in particular suitable for theproduction of urea-based granules, such as granules of urea, ureaammonium nitrate, urea ammonium sulphate and urea doped with elementalsulphur.

An exemplary embodiment of a fluidized bed reactor according to theinvention will be explained with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1: shows an exemplary fluidized bed reactor setup according to theinvention. This system has being realized by Yara International ASA in asemi-industrial pilot plant (SIPP) in Sluiskil, The Netherlands.

FIG. 2: shows a pressure graphs of the pressure in a fluidized bedreactor setup with two ventilators in different operational modes.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

FIG. 1 shows an exemplary embodiment of a fluidized bed reactor 1 forthe production of urea granules, or ammonium nitrate granules. Thefluidized bed reactor 1 as shown in the figure comprises threegranulation compartments 2, 3, 4 for granulation and two after-coolercompartments 5, 6 for subsequent cooling and drying the granules.

The first granulation compartment 2 of the fluidized bed reactor 1comprises an inlet 7 for the supply of nuclei. Opposite to the inlet 7is a first passage 8, leading to the second compartment 3. The secondcompartment 3 comprises a second passage 9 opposite to the first passage8 and leading to the third compartment 4. The third compartment 4comprises an outlet 10 opposite to the second passage 9. As a result,the nuclei can flow from the inlet 7 to the outlet 10 in a straight flowpath.

The fluidized bed reactor 1 comprises a floor 12 made of a grid whichsupports a bed 13 of nuclei and which permits the passage of ambientfluidization air, supplied from a space 14 below the grid floor 12. Airinlets can for example be located at a side wall of the space 14 belowthe grid 12 and/or in the bottom of that space 14. In case the ambientair is relatively cold, for example during winter, the air can bepreheated by heaters 15 in or upstream the space 14. The heated airfluidizes the bed 13 of nuclei.

The space 14 below the grid floor 12 is divided into compartments 17,18, 19 in line with the compartments 2, 3, 4 above the grid floor 12. Ineach of the compartments 2, 3, 4 the grid floor 12 of the fluidized bedreactor 1 is provided with clusters of air-assisted sprayers 21projecting above grid floor 12. The sprayers 22 are fed with a flow ofliquid product (e.g. urea or ammonium nitrate) (F1) and a flow ofpressurized air (F2), and spray an aqueous solution of urea or ammoniumnitrate into the fluidized bed 13. In the granulator compartments 2, 3,4, the water of the sprayed urea or ammonium nitrate solution evaporatesand urea crystallizes on the nuclei, which grow to form granules.

The after-cooler is integrated into the fluidized bed reactor andcomprises a fluidized bed cooler with a grid floor 12′ supporting a bed13′ of freshly produced granules and a space 20, 21 below the grid floorin line with the compartments 5 and 6 above the grid floor 12, alsosupplied with a heater 23 for the supply of air fluidizing and dryingthe bed 13′.

The after-cooler is provided with an outlet 24 for discharging the driedand cooled granules. Subsequently (not shown), undersized and oversizedgranules are separated from granules of the desired size, which aredischarged for storage. The oversized granules can be crushed to finerparticles, which can be recycled together with the undersized particles.

Air and air borne dust particles are discharged from the granulatorcompartments 2, 3, 4 and the after-cooler compartments 5 and 6 via oneor more air ducts 25 to at least one scrubbers 28. In the schematicdrawing of FIG. 1 a single scrubber is shown. Separate scrubbers may beused for treating air from the granulation compartments and air from thecooler, respectively. The scrubber may be a wet scrubber.

In the scrubber 28 the air is stripped. Separated dust particles can berecycled to the granulator compartments 2, 3, 4 via one or more ducts27. Clean air leaves the scrubber 28 via a discharge duct 29 comprisingan exhaust fan 30.

The exhaust fan 30 creates a pressure drop of about 10 and 100 mbar,e.g., about 75 mbar over the full flow path from the grid floor 12, 12′to the exhaust fan 30. As a result, fluidization air is sucked into thegranulation compartments 2, 3, 4 via the grid floors 12 and 12′. Noadditional blowers are provided. The difference with known systems isshown in FIG. 2. FIG. 2 shows a pressure graphs of the pressure in asystem, with either a downstream ventilator active (this application,C), an upstream ventilator active (A), or both an upstream ventilatorand a downstream ventilator active (B) active such that a smallunderpressure (0.1 to 10 mbar) is formed in the fluidized bed reactor,as disclosed in U.S. Pat. No. 5,779,945 (DSM N.V., 1998) and EP 2253374A1 (Stamicarbon, 2010). It is obvious that in the setup according tothis invention, a larger underpressure is formed in the fluidized bedreactor, typically between 10 and 60 mbar.

Example

A setup of the fluidized bed reactor according to the invention withthree granulation compartments and integrated after-cooler was used forthe continuous production of ammonium nitrate granules (see FIG. 1). Theparameters of the experiment are summarized in the Tables 1 and 2 below.These are typical parameters for the operation of the fluidized bedreactor according to the invention.

TABLE 1 Average material balance After 7 Units Start hours After 13.5hours Outflow kg/h 11,775 11,385 11,221 granulator Ready product kg/h7,660 7,520 7,380 after sieving Fines after kg/h 2,782 2,388 2,784sieving (returned to granulator) Coarse after kg/h 1,308 1,452 1,032sieving (to be crushed) Product after kg/h 1,308 1,452 1,032 crushingDust at exit kg/h n.m. n.m. n.m. granulator Dust after kg/h n.m. n.m.n.m. ventilator Agglomerates kg/h 25 25 25 n.m. not measured

TABLE 2 Process parameters Ammonium nitrate solution Temperature 178 °C. Concentration 97.6 % Flow rate 5.5 m³/h Pre-pressure 2.0 ato¹ Pernebulizer 1st about m³/h compartment 0.561 Number of nebulizer: 4 Pernebulizer 2th about m³/h compartment 0.360 Number of nebulizer: 5 Pernebulizer 3th about m³/h compartment 0.291 Number of nebulizer: 5Injection air Temperature 142 ° C. Pressure 0.52 ato Flow rate aboutNm³/h 1,800 Per nebulizer 1st about 130 Nm³/h compartment Number ofnebulizer: 4 Per nebulizer 2th about 130 Nm³/h compartment Number ofnebulizer: 5 Per nebulizer 3th about 130 Nm³/h compartment Number ofnebulizer: 5 Fluidization air Temperature Flow rate Speed (° C.) (Nm³/h)Nm/sec 1st compartment 78 2,471 2.02 2d compartment 81 2,359 1.93 3dcompartment 79 2,836 2.92 4th compartment 20 2,235 5th compartment 182,299 Suction 113 about 14,000 Fluidized bed Height 685 mmwk²Temperature 1st compartment 127 ° C. Temperature 2d compartment 127 ° C.Temperature 3d compartment 130 ° C. Temperature 4th compartment n.m. °C. Temperature 5th compartment 119 ° C. Temperature after granulator 119° C. Expansion room (space over the granulator compartments) Temperature1st compartment 127 ° C. Temperature 2d compartment 130 ° C. Temperature3d compartment 127 ° C. Temperature 4th + 5th n.m. ° C. compartmentTemperature top granulator 113 ° C. ¹atmospheres of overpressure overthe standard atmospheric pressure; n ato = n + 1 atm (absolute) ≈ n + 1bar ²mmwk = mm water column; 1 mmwk = 0.0981 mbar ≈ 0.1 mbar

RESERVATIONS

Although the subject matter has been described in language, specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter as defined in the appended claims is notnecessarily limited to the specific features or acts described above ashas been held by the courts. Rather, the specific features and actsdescribed above are disclosed as example forms of implementing theclaims. The claimed subject matter is not limited to implementationsthat solve any or all disadvantages noted in the background.

1. A fluidized bed reactor comprising at least one granulation compartment with one or more air inlets, and at least one air moving device downstream the granulation compartment configured to draw air through said one or more air inlets into the granulation compartment.
 2. The fluidized bed reactor according to claim 1, comprising a scrubber downstream the granulation compartment, wherein the at least one air moving device is downstream the scrubber.
 3. The fluidized bed reactor according to claim 1 comprising at least one after-cooler and the at least one an air moving device downstream the after-cooler.
 4. The fluidized bed reactor according to claim 3, comprising a scrubber downstream the after-cooler, the at least one air moving device being positioned downstream the scrubber.
 5. The fluidized bed reactor according to claim 1, wherein the air moving device comprises one or more exhaust fans for discharging air.
 6. A method for producing granules using a fluidized bed reactor comprising at least one granulation compartment having one or more air inlets and a bed of granules, and at least one air moving device downstream the granulation compartment, the method comprising: drawing air in the at least one granulation compartment through the one or more air inlets using the at least one air moving device; and fluidizing the bed of granules with the drawn in air.
 7. The method of claim 6, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the one or more air inlets and an air exhaust below 800 mm water column.
 8. The method of claim 7, wherein the pressure drop is below 750 mm water column.
 9. The method according to claim 6, wherein the pressure drop over the granulation compartment is at most 500 mm water column.
 10. The method according to claim 6, wherein the bed of granules include urea granules.
 11. The method according to claim 6, wherein the bed of granules include ammonium nitrate granules.
 12. A fluidized bed reactor comprising at least one granulation compartment with at least one air inlets and at least one air moving device, configured to move air through said at least one air inlet into said at least one granulation compartment, characterized in that said air is moved essentially by the action of said at least one air moving device downstream of said granulation compartment.
 13. The fluidized bed reactor according to claim 12, devoid of any air moving device which is configured to move air through said at least one air inlet into said granulation compartment and which is positioned upstream of the granulation compartment.
 14. The fluidized bed reactor according to claim 12, comprising at least one after-cooler wherein the at least one air moving device is positioned downstream of the at least one after-cooler.
 15. The fluidized bed reactor according to claim 14, wherein the at least one after-cooler is integrated in the fluidized bed reactor as a set of at least two compartments subsequent to the granulation compartments.
 16. The fluidized bed reactor according to claim 12, comprising at least one scrubber downstream of the at least one granulation compartment, wherein the at least one air moving device is positioned downstream of the at least one scrubber.
 17. The fluidized bed reactor according to claim 14, further comprising at least one scrubber downstream of the at least one after-cooler, wherein the at least one air moving device is positioned downstream of the at least one scrubber.
 18. The fluidized bed reactor according to claim 12, wherein the at least one air moving device comprises at least one exhaust fan for discharging air.
 19. A method for the production of granules using a fluidized bed reactor comprising at least one granulation compartment with at least one air inlets and at least one air moving device, configured to move air through said at least one air inlet into said at least one granulation compartment, wherein said air is moved essentially by the action of said at least one air moving device downstream of said granulation compartment, the method comprising: drawing air in the at least one granulation compartment through the at least one air inlet using the at least one air moving device; and fluidizing the bed of granules with said drawn in air.
 20. The method according to claim 19, devoid of any air moving step by an air moving device which is configured to move air through said at least one air inlet into said granulation compartment and which is positioned upstream of the granulation compartment.
 21. The method according to claim 19, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the at least one air inlet and an air exhaust of between 10 and 100 mbar.
 22. The method according to claim 21, wherein the pressure drop is between 10 and 80 mbar.
 23. The method according to claim 19, wherein drawing air in the at least one granulation compartment includes creating a pressure drop over the granulation compartment of between 10 and 60 mbar.
 24. The method according to claim 19, wherein the air drawn into the at least one granulation compartment is not preheated, either deliberately using pre-heating equipment, or as a side effect of the action of upstream equipment.
 25. The method according to claim 19, wherein the bed of granules include urea-based granules.
 26. The method according to claim 19, wherein the bed of granules include ammonium nitrate-based granules.
 27. The method according to claim 25, wherein the urea based granules are urea, urea ammonium nitrate, urea ammonium sulphate or urea doped with elemental sulphur.
 28. The method according to claim 26, wherein the ammonium nitrate-based granules are ammonium nitrate granules or calcium nitrate granules.
 29. A fluidized bed reactor comprising at least one granulation compartment with one or more air inlets; at least one scrubber downstream from the at least one granulation compartment; at least one air duct between the at least one granulation compartment and the at least one scrubber; and at least one air moving device downstream from the at least one granulation compartment, wherein when a fluid bed is present in the at least one granulation compartment, the at least one air moving device has or devices have sufficient capacity to create a vacuum exceeding the total pressure drop between the one or more air inlets and the at least one air moving device.
 30. The fluidized bed reactor according to claim 29, wherein the at least one air moving device is downstream from the scrubber.
 31. The fluidized bed reactor according to claim 29, further comprising at least one after-cooler downstream from the at least one granulation compartment.
 32. The fluidized bed reactor according to claim 31, wherein the after-cooler is upstream from a scrubber and the at least one air moving device is positioned downstream from the scrubber.
 33. The fluidized bed reactor according to claim 31, wherein the air moving device comprises one or more exhaust fans for discharging air.
 34. A method for producing granules using a fluidized bed reactor comprising at least one granulation compartment having one or more air inlets and a bed of granules, at least one scrubber downstream from the at least one granulation compartment, at least one air duct between the at least one granulation compartment and the at least one scrubber, and at least one air moving device downstream from the at least one granulation compartment, the method comprising fluidizing the bed of granules by drawing air into the at least one granulation compartment through the one or more air inlets using the at least one air moving device, wherein the air drawn into the at least one granulation compartment is not heated by a blower upstream from the one or more air inlets.
 35. The method of claim 34, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the one or more air inlets and an air exhaust below 800 mm water column.
 36. The method of claim 35, wherein the pressure drop is below 750 mm water column.
 37. The method according to claim 34, wherein the pressure drop over the granulation compartment is at most 500 mm water column.
 38. The method according to claim 34, wherein the bed of granules include urea granules.
 39. The method according to claim 34, wherein the bed of granules include ammonium nitrate granules.
 40. A method for producing fertilizer granules by crystallization of urea and/or ammonium nitrate, using a fluidized bed reactor comprising at least one granulation compartment with one or more air inlets and a bed of granules, at least one scrubber downstream from the at least one granulation compartment, at least one air duct between the at least one granulation compartment and the at least one scrubber, and at least one air moving device downstream from the at least one granulation compartment, the method comprising fluidizing the bed of granules by drawing air into the at least one granulation compartment through the one or more air inlets using the at least one air moving device, wherein the air drawn into the at least one granulation compartment is not heated by a blower upstream from the one or more air inlets. 